ORAU TEAM

Dose Reconstruction

Project for NIOSH

Oak Ridge Associated Universities I Dade Moeller & Associates I MJW Corporation

Page 1 of 29

Document Title:

Nevada Test Site – Occupational Medical Dose

Document Number: ORAUT-TKBS-0008-3 

Revision: 01

Effective Date: 06/22/2007

Type of Document: TBD

Supersedes: Revision 00

Subject Expert(s): Ronald L. Kathren

Site Expert(s): Vernon E. Shockley

Approval: Signature on File Approval Date: 06/04/2007

Eugene M. Rollins, Document Owner

Approval: Signature on File Approval Date: 06/04/2007

John M. Byrne, Task 3 Manager

Concurrence: Signature on File Concurrence Date: 06/05/2007

Edward F. Maher, Task 5 Manager

Concurrence: Signature on File Concurrence Date: 06/12/2007

Kate Kimpan, Project Director

Approval: Brant A. Ulsh Signature on File for Approval Date: 06/22/2007

James W. Neton, Associate Director for Science

 New Total Rewrite Revision Page Change

FOR DOCUMENTS MARKED AS A TOTAL REWRITE, REVISION, OR PAGE CHANGE, REPLACE THE PRIOR 

REVISION AND DISCARD / DESTROY ALL COPIES OF THE PRIOR REVISION.
Document No. ORAUT-TKBS-0008-3 Revision No. 01 Effective Date: 06/22/2007 Page 2 of 29

PUBLICATION RECORD

EFFECTIVE 

DATE

REVISION 

NUMBER DESCRIPTION

06/09/2004 00 New technical basis document for the Nevada Test Site –

Occupational Medical Dose. Incorporates internal review and NIOSH 

comments. First approved issue. Initiated by Eugene M. Rollins.

06/22/2007 01 Approved revision initiated to concur with ORAUT-OTIB-0006 

(ORAUT 2005), current data in other TBDs, and to include new legal 

wording in Section 3.1. Constitutes a total rewrite of the document. 

Incorporates formal internal and NIOSH review comments. Adds 

Attributions and Annotations section. This revision results in no 

change to the assigned dose and no PER is required. Training 

required: As determined by the Task Manager. Initiated by Vernon 

E. Shockley.
Document No. ORAUT-TKBS-0008-3 Revision No. 01 Effective Date: 06/22/2007 Page 3 of 29

TABLE OF CONTENTS

SECTION TITLE

Acronyms and Abbreviations ...............................................................................................................

PAGE

4

3.1 Introduction................................................................................................................................. 6

3.1.1 Purpose ...........................................................................................................................7

3.1.2 Scope..............................................................................................................................7

3.2 Technical Factors That Affect Medical X-Ray Dose .................................................................... 7

3.2.1 Applied Kilovoltage and Filtration ....................................................................................7

3.2.2 Current and Exposure Time.............................................................................................9

3.2.3 Distance ........................................................................................................................10

3.2.4 Collimation and Waveform Characteristics ....................................................................10

3.2.5 Screens, Grids, and Other Factors That Can Affect Worker Dose ................................. 11

3.3 X- Ray Doses from 1951 to Present.......................................................................................... 12

3.3.1 Doses from Posterior-Anterior Chest Radiography ........................................................14

3.3.2 Lateral 14- by 17-in. Chest Radiography .......................................................................16

3.4 Uncertainty Analysis for Radiography Doses ............................................................................ 17

3.5 Attributions and Annotations ..................................................................................................... 19

References ........................................................................................................................................24

Glossary ............................................................................................................................................27

LIST OF TABLES

TABLE TITLE

3-1 Relationship of beam intensity and various technique factors ...................................................

PAGE

11

3-2 Analogues for IREP organs not in ICRP Publication 34.............................................................13

3-3 Frequency of PA and LAT chest X-rays at NTS ........................................................................14

3-4 Beam parameters for 14- by 17-in. PA chest radiography .........................................................14

3-5 Substitute DCFs for PA and LAT chest projections assuming a minimally collimated 

beam.........................................................................................................................................15

3-6 Organ doses from PA and LAT chest X-rays at NTS from 1951 to present ............................... 15
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ACRONYMS AND ABBREVIATIONS

CFR Code of Federal Regulations

cGy centigray

cm centimeter

DCF dose conversion factor

DOE U.S. Department of Energy

EEOICPA Energy Employees Occupational Illness Compensation Program Act of 2000

ESE entrance skin exposure

Gy gray

HVL half-value layer

ICRP International Commission on Radiological Protection

ICRU International Commission on Radiation Units and Measurements

in. inch

IREP Interactive RadioEpidemiological Program

keV kiloelectron-volt, 1,000 electron-volts

kVp peak kilovoltage, applied kilovoltage

LAT lateral

mA milliampere

mAs milliampere-second

mGy milligray

mm millimeter

mm Al millimeters of aluminum

mrad millirad 

mR milliroentgen

mrem millirem

NCRP National Council on Radiation Protection and Measurement

NIOSH National Institute for Occupational Safety and Health

NTS Nevada Test Site

ORAU Oak Ridge Associated Universities

PA posterior–anterior

POC probability of causation

R roentgen

RMS root mean square

s second

SID source-to-image distance

SRDB Ref ID Site Research Database Reference Identification (number)

SSD source-to-skin distance

TBD technical basis document
Document No. ORAUT-TKBS-0008-3 Revision No. 01 Effective Date: 06/22/2007 Page 5 of 29

U.S.C. United States Code

§ section or sections
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3.1 INTRODUCTION

Technical basis documents and site profile documents are not official determinations made by the 

National Institute for Occupational Safety and Health (NIOSH) but are rather general working 

documents that provide historic background information and guidance to assist in the preparation of 

dose reconstructions for particular sites or categories of sites. They will be revised in the event 

additional relevant information is obtained about the affected site(s). These documents may be used 

to assist NIOSH staff in the completion of the individual work required for each dose reconstruction.

In this document the word “facility” is used as a general term for an area, building, or group of 

buildings that served a specific purpose at a site. It does not necessarily connote an “atomic weapons 

employer facility” or a “Department of Energy [DOE] facility” as defined in the Energy Employees 

Occupational Illness Compensation Program Act [EEOICPA; 42 U.S.C. § 7384l(5) and (12)]. 

EEOICPA defines a DOE facility as “any building, structure, or premise, including the grounds upon 

which such building, structure, or premise is located ... in which operations are, or have been, 

conducted by, or on behalf of, the Department of Energy (except for buildings, structures, premises, 

grounds, or operations ... pertaining to the Naval Nuclear Propulsion Program)” [42 U.S.C. 

§ 7384l(12)]. Accordingly, except for the exclusion for the Naval Nuclear Propulsion Program noted 

above, any facility that performs or performed DOE operations of any nature whatsoever is a DOE 

facility encompassed by EEOICPA.

For employees of DOE or its contractors with cancer, the DOE facility definition only determines 

eligibility for a dose reconstruction, which is a prerequisite to a compensation decision (except for 

members of the Special Exposure Cohort). The compensation decision for cancer claimants is based 

on a section of the statute entitled “Exposure in the Performance of Duty.” That provision [42 U.S.C. 

§ 7384n(b)] says that an individual with cancer “shall be determined to have sustained that cancer in 

the performance of duty for purposes of the compensation program if, and only if, the cancer ... was 

at least as likely as not related to employment at the facility [where the employee worked], as

determined in accordance with the POC [probability of causation1

As noted above, the statute includes a definition of a DOE facility that excludes “buildings, structures, 

premises, grounds, or operations covered by Executive Order No. 12344, dated February 1, 1982 

(42 U.S.C. 7158 note), pertaining to the Naval Nuclear Propulsion Program” [42 U.S.C. § 7384l(12)]. 

While this definition contains an exclusion with respect to the Naval Nuclear Propulsion Program, the 

section of EEOICPA that deals with the compensation decision for covered employees with cancer 

[i.e., 42 U.S.C. § 7384n(b), entitled “Exposure in the Performance of Duty”] does not contain such an 

exclusion. Therefore, the statute requires NIOSH to include all occupationally derived radiation 

exposures at covered facilities in its dose reconstructions for employees at DOE facilities, including 

radiation exposures related to the Naval Nuclear Propulsion Program. As a result, all internal and 

external dosimetry monitoring results are considered valid for use in dose reconstruction. No efforts 

are made to determine the eligibility of any fraction of total measured exposure for inclusion in dose 

reconstruction. NIOSH, however, does not consider the following exposures to be occupationally 

derived:

] guidelines established under 

subsection (c) ...” [42 U.S.C. § 7384n(b)]. Neither the statute nor the probability of causation

guidelines (nor the dose reconstruction regulation) define “performance of duty” for DOE employees 

with a covered cancer or restrict the “duty” to nuclear weapons work.

• Radiation from naturally occurring radon present in conventional structures

• Radiation from diagnostic X-rays received in the treatment of work-related injuries

 

1 The U.S. Department of Labor is ultimately responsible under the EEOICPA for determining the POC. 
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3.1.1

The purpose of this TBD is to describe Nevada Test Site (NTS) occupational medical X-ray systems 

and practices. The Oak Ridge Associated Universities (ORAU) Team will use this information as 

needed to evaluate medical X-ray doses for EEOICPA claims.

Purpose

3.1.2

This TBD describes the technical aspects of dose reconstruction from medical X-rays administered 

prior to employment and periodically thereafter as a condition of employment. 

Scope

Attributions and annotations, indicated by bracketed callouts and used to identify the source, 

justification, or clarification of the associated information, are presented in Section 3.5. 

3.2 TECHNICAL FACTORS THAT AFFECT MEDICAL X-RAY DOSE

A number of factors determine the dose to workers from a medical X-ray procedure. For a standard 

medical radiographic unit with a tungsten target (anode) and focal spot of 1 to 2 mm, these factors 

include the basic machine settings used for the exposure, which include the applied kilovoltage of the 

beam (kVp, also known as peak kilovoltage), beam current in milliamperes, time of exposure in 

seconds, distance in centimeters, waveform, amount and kind of filtration used, collimation or use of 

diaphragms, tube housing characteristics, type and speed of the film, development procedures, 

screens, grids, and the size of the worker. In the absence of direct measurements of the beam itself 

(which are rarely available), the dose to the worker can be estimated with a reasonable degree of 

accuracy from knowledge of the following three basic machine parameters: (1) applied kilovoltage, 2) 

current, and 3) exposure time with assumptions about filtration, collimation, and waveform 

characteristics ORAUT (2005). The following sections discuss the implications of these factors to 

worker dose. However, if X-ray exposure or dose measurements are available, as they are for some 

NTS procedures, these should be used in the development of organ doses.

3.2.1

The energy of the X-ray beam, sometimes referred to as beam quality, is determined by the applied 

kilovoltage and the filtration. X-rays produced in a typical medical X-ray tube are bremsstrahlung and, 

as such, are a distribution or spectrum of energies ranging from zero to the applied kilovoltage, which 

refers to the potential between the anode and cathode of the tube. For a typical unfiltered X-ray 

spectrum, the average energy is about one-third of the peak or maximum X-ray energy, which is equal 

to the applied kilovoltage. Therefore, most of the produced X-rays are much lower in energy than the 

applied kilovoltage of the beam. In addition, they are attenuated by the torso or other portion of the 

body being radiographed, and most never reach the film. These low-energy X-rays are of little value 

in radiography but contribute significantly to worker dose BRH (1970, pp. 159–160). 

Applied Kilovoltage and Filtration

To reduce the dose to the worker, filtration in the form of a specified thickness of absorbing material is 

added to the beam port. This has the net effect of absorbing a large fraction of the lower energy 

X-rays that are of little or no value in making the radiograph while allowing most of the more energetic 

and radiographically useful X-ray photons to pass. In this manner, the dose to the worker is reduced 

significantly and radiographic quality can be enhanced. A filtered X-ray spectrum has a 

correspondingly higher average energy than before it was filtered, even though the photon fluence 

rate and corresponding dose rate is much reduced. Such a beam is said to have been hardened. A 

corollary to this filtration technique is to use a higher applied kilovoltage and to filter the beam 
Document No. ORAUT-TKBS-0008-3 Revision No. 01 Effective Date: 06/22/2007 Page 8 of 29

relatively heavily to stop most of the low-energy (radiographically useless) photons from reaching the 

worker (ICRP Publication 34; ICRP 1982, p. 25, Tables A2–A8). 

Beam energy is specified in terms of quality, or hardness, which in turn, can be specified in terms of 

the half-value layer (HVL) in millimeters of aluminum (mm Al). This parameter is, unfortunately, 

seldom available. Even if it is known, it is of limited value in part because it does not specify the 

maximum energy of the beam or its true quality because, as the HVL measurement is made, the 

absorbers act as filters and the beam is further hardened. Therefore, the first HVL is always smaller 

than the second, which in turn is smaller than the third, and so forth. What is commonly, but not 

always available is the peak or applied kilovoltage of the machine and the external or added filtration. 

All X-ray tubes have so-called inherent filtration, which is the window, aperture, or port in the tube 

enclosure through which the X-ray beam emerges from the X-ray tube. In medical diagnostic units, 

the window or beam port is purposely made very thin, typically equivalent to 0.5 mm Al in attenuation, 

which provides little beam hardening. Other than the beam port itself, the tube housing is shielded to 

eliminate leakage radiation from the tube. Therefore, the beam port effectively characterizes what 

could be considered the inherent collimation of the tube (DeMarre 2002; Geiger et al. 1960). 

Although the benefits of filtration with respect to improved radiographic images were known and 

understood as early as March 1896 [within months of the discovery of X-rays (Magie 1896)], initial 

diagnostic radiographs were made with no added filtration. Recommendations made in 1937 by the 

International Commission on Radiation Units and Measurements, although not specific for thickness, 

specified aluminum filters for X-rays of 20 to 120 kVp (which incorporates the diagnostic X-ray energy 

range) (ICRU 1937). Typical external filtration in the 1940s ranged from none to 1 mm Al. This was 

in line with recommendations of the U.S. Advisory Committee on X-Ray and Radium Protection [later 

the National Council on Radiological Protection and Measurement (NCRP)], which called for 0.5 mm 

Al for radiographic installations and 1 mm Al for fluoroscopy (NBS 1936). In 1949, the NCRP 

recommended 1-mm Al filtration for radiography of thick parts of the body such as the chest (NBS 

1949); this thickness was used during World War II in 100-mA units in larger military hospitals, and 

presumably at NTS as well (Olson, Trask, and Dessen 1966). Recommended thicknesses were later 

increased not only for worker protection but also for improved radiographic image quality. In 1955, 

the NCRP recommendation for diagnostic X-ray units called for 2-mm Al filtration for new machines 

(NBS 1955). This increased in 1968 to 2.5 mm Al for medical diagnostic units above 70 kVp (NCRP 

1968). For operating machines, these recommended filter thicknesses might not have been 

implemented for some time after the date of the recommendation, especially if the installed machines 

did not exhibit changes in effectiveness and continued to operate without apparent problems.

The relationship of beam intensity2 to peak kilovoltage and filtration is complex and to some extent 

machine-specific. Therefore, the relationship is best determined empirically. However, in the 

absence of empirical data for a specific machine, adequate contemporary empirical and theoretical 

data exist on which to determine machine output with a reasonable degree of uncertainty. Additional 

filtration reduces the entrance skin exposure3

 

2 In this document, beam intensity refers to the output of the machine in terms of exposure in the special sense per 

milliampere-second. Exposure in the special sense is referenced to ionization in air and, as such, is not a dose quantity. 

(ESE) in a generally exponential manner. For a typical 

single-phase, half-, full-, or self-rectified machine operating in the diagnostic range of 80 to 100 kVp, 

each additional millimeter of Al filtration will effect a reduction of about 40% in the ESE (Trout, Kelley, 

and Cathey 1952; Taylor 1957). Therefore, the approximate intensity reduction afforded by any 

thickness of Al filtration can be determined by the following exponential equation: 

3 Throughout this document, italics are used to differentiate exposure in the special sense from exposure in the general 

sense. A brief discussion of both the general and special senses can be found in many publications including NCRP (1985) 

and ICRU (1998). The definition and application of the quantity exposure and its concomitant unit the roentgen have 

undergone several important modifications over the years, which have been documented throughout the literature.
Document No. ORAUT-TKBS-0008-3 Revision No. 01 Effective Date: 06/22/2007 Page 9 of 29

I = Ioe-0.4t (3-1)

or

ln (I/Io) = -0.4t

where

t = mm Al

I = beam intensity with filter

Io = beam intensity without filter

In the absence of specific measurements or empirical data, this correction can be applied to 

determine the effect of filtration on beam intensity, and is consistent with the guidance put forth in

OCAS-IG-001, External Dose Reconstruction Implementation Guideline (NIOSH 2006).

Increasing the kilovoltage will increase the beam intensity or exposure rate. This can be calculated 

using Kramer’s Rule, but such calculations are difficult, complex, and time-consuming, and the best 

results are approximations. However, many empirical studies of beam intensity as a function of 

kilovoltage provide ample credible evidence to show that, for a given amount of filtration, increasing 

the applied kilovoltage will increase the beam intensity according to the 1.7 power of the applied 

kilovoltage (Handloser and Love 1951; Trout, Kelley, and Cathey 1952; Kathren 1965; BRH 1970). In 

the absence of specific measurements or empirical data, this function can be applied to determine the 

effect of applied kilovoltage on beam intensity. This method is fully consistent with the guidance in

OCAS-IG-001 (NIOSH 2006).

It should be noted that the effects of filtration and applied kilovoltage tend to offset one another; 

addition of filtration reduces the exposure or dose per milliampere-seconds, while increasing the 

applied kilovoltage increases the exposure and dose per milliampere-second. Higher applied 

kilovoltage radiographic techniques typically require shorter exposures in terms of milliampereseconds, and the dose reduction from additional filtration at the recommended level more than offsets 

the additional dose from using increased applied kilovoltage. However, there is no direct 

correspondence or proportionality between the effects of filtration and applied kilovoltage (Trout, 

Kelley, and Cathey 1952; ORAUT 2005). 

3.2.2

X-ray exposures are typically specified in terms of milliampere-seconds, the product of X-ray tube 

current and exposure time. Therefore, other factors remaining equal (e.g., kilovoltage, filtration, film, 

development, and screen combination), radiation exposure is proportional to the number of 

milliampere-seconds. The current in an X-ray tube refers to the number of electrons accelerated 

across the evacuated volume of the tube and flowing from the cathode to the anode. In theory, the 

number of X-ray photons produced (and therefore the exposure) will be directly proportional to the Xray tube current for a given applied kilovoltage. This is and has been true for most medical 

radiography units over their design tube current range (Gray 1996; Sante 1946, 1954; Thomas 1959; 

ORAUT 2005). Data from beam measurements made with medical X-ray units at NTS over the years 

are indicative of this linearity. Therefore, in the absence of measurements before 1957 or other 

information to the contrary, it is reasonable and consistent with long-standing radiographic practice 

(Sante 1946, p.61) to assume linearity of exposure with tube current for a given applied kilovoltage 

and filtration [1]. 

Current and Exposure Time
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Exposure time is the time that the tube was energized (i.e., the machine was producing X-rays) and is 

for all practical purposes, linear with exposure. To avoid or minimize image blurring from the beating 

heart, the exposure time for chest radiography was minimized, and the current proportionately 

increased to obtain the desired exposure. However, earlier medical radiographic units were equipped 

with mechanical timers with accuracy that was not as good as the electronic timers used on later 

machines. Gross bias errors in timer accuracy are unlikely because they would have resulted in an 

over- or underexposure of the radiograph and so would have been quickly detected and corrected. 

Subtler are small random errors that can produce uncertainties of perhaps ±20% in the exposure [2]. 

However, the limited measurement data available from NTS medical X-ray units give no indication or 

suggestion that time or exposure parameters might be subject to error. No evidence has been found 

to suggest or verify that chest photofluorography, which resulted in much greater doses than a 

standard radiographic procedure, was performed for the NTS workers [3]. 

3.2.3

X-ray beam intensity is a function of distance from the target and approximates the inverse square at 

large distances from the tube. Radiographic chest films were taken at a standard source-to-image 

distance (SID)

Distance

4

To compensate for the increased attenuation provided by a larger worker, X-ray technicians would 

sometimes increase the beam settings or, if the machine was so equipped, might use a high-speed 

Potter-Bucky diaphragm (known as a Bucky), probably with a somewhat higher applied kilovoltage. 

However, because chest thickness is rarely recorded at the time of each X-ray, organ dose 

reconstruction is based on the average worker’s chest size, which is 22 to 24 cm (DeMarre 2002–

2003; Sante 1946,1954). 

of 72 in. Source refers to the focal spot of the tube, and image refers to the plane of 

the film. The distance to the worker, sometimes expressed in terms of the source-to-skin distance 

(SSD), who was between the source and the film cassette, was somewhat smaller and, therefore, the 

ESE to the worker was somewhat greater than the exposure at the plane of the film. In addition, 

worker attenuation would further reduce or attenuate the number of photons that reached the film

(Sante 1954; Geiger et al. 1960). 

3.2.4

Collimation and waveform characteristics are among the factors that affect dose. X-ray waveforms 

used in medical screening were half-wave rectified, which is almost never seen, and full-wave 

rectified, which is typical of medical radiographic units and characteristic of the units used at NTS

[4]. A half-wave rectified machine produces 60 half-sinusoidal pulses of X-rays per second, each with 

a duration of 1/120 of a second. A full-wave rectified machine produces 120 half-sinusoidal pulses 

per second, each with a duration of 1/120 of a second. Therefore, for a given setting of applied 

kilovoltage and milliamperes, the intensity of the beam from a half-wave rectified machine is half that 

of the beam from a full-wave rectified machine (Sante 1946, 1954). A third waveform, constant 

potential, was available at the time of initial operation at the NTS and is defined in NCRP Report 33 

(NCRP) 1968. The constant potential waveform machine was not used at the NTS [5].

Collimation and Waveform Characteristics

For NTS, waveform is of minor significance in relation to reconstruction of worker exposure because 

actual output measurement data are available from 1957 to 1992 [6]. Before 1957, machine 

techniques are not available, and estimates of X-ray exposures are based on references providing 

median dose for 1950 to 1957 (Gray 1996). 

 

4 Also known as film-to-focus distance.
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Collimation refers to the size of the beam. Early radiographic practices used a fairly large aperture 

with limited collimation to ensure that the radiograph included the entire area of interest. Later, 

because of protection concerns, beams were collimated so the smallest beam consistent with the 

area of interest was used, which thereby limited the exposed area of the worker and, in the case of 

chest radiography, lowered doses to organs such as gonads, thyroid, and gastrointestinal tract. A 

practical check of collimation can be made by reference to the radiograph: A well-collimated beam 

leaves a small unexposed area at the edges of the radiograph, while a poorly collimated beam 

produces a radiograph that is exposed over all of its area (Geiger et al. 1960; DeMarre 2002–2003). 

Available data, including direct beam measurements, indicate that X-ray beams used at NTS were 

well collimated (Kathren and Shockley 2003). However, this analysis includes the favorable to 

claimant assumption that minimal collimation occurred before January 1, 1957. Therefore, the 

substitute dose conversion factors (DCFs) in Table 3-5 were used to estimate organ doses prior to 

January 1, 1957. (See Section 3.3 and Table 3-6) (Taulbee 2004). 

3.2.5

A number of other factors affect the X-ray exposure required to obtain a proper radiograph and, 

therefore, the dose to the worker. Knowledge of these factors is not necessary for dose 

reconstruction if beam measurements are available or if the primary machine characteristics of 

applied kilovoltage, exposure time, and current are known, along with the amount of primary beam 

filtration. For completeness, this document briefly mentions these factors, which are tube housing, 

film type, film speed, development procedure, screens, and grids.

Screens, Grids, and Other Factors That Can Affect Worker Dose

X-ray tubes used for medical radiography are typically enclosed in protective lead or shielded tube 

housings with the primary beam brought out through a port or window in the side of the housing. 

Although some reduction of the dose to the worker is achieved, largely through elimination of 

scattered radiation and improved collimation, the primary purpose of this tube housing is the 

protection of the operator, unexposed X-ray film, and nearby individuals other than the worker. This 

issue is moot, however, because virtually all X-ray tubes, and certainly those used at NTS, had 

protective tube housings (DeMarre 2002, 2002–2003). 

The amount of exposure needed for a suitably exposed radiograph is affected by film speed and 

development. Fine-grained (slow) emulsions produce a superior radiographic image but require 

additional exposure in comparison to course-grained (fast) films. In addition, underdevelopment of 

film requires additional exposure to achieve satisfactory radiographic quality. Intensifying screens are 

used within the cassette to intensify the radiographic effect and thereby increase film speed and 

reduce worker dose. Grids, specifically the Potter-Bucky diaphragm or grid (colloquially known as the 

Bucky), are sometimes used for thick-section radiography but rarely for chest radiography, except with 

large workers (Sante 1954, pp. 212–224a; Thomas et al. 1959). 

For convenience and possible application to cases, Table 3-1 lists the effects of various technique 

factors on beam intensity. However, all of the parameters discussed in this section are factored into 

the technique (i.e., applied kilovoltage and current) that is used and, with the exception of rare 

instances and a virtually complete absence of other data, are not important to dose reconstruction

NIOSH (2006). 

Table 3-1. Relationship of beam intensity and various technique factors.

a

Parameter Units Relationship with intensity

Applied voltage kVp Intensity proportional to 1.7 power of kVp

Tube current mA Linear

Exposure time s Linear
Document No. ORAUT-TKBS-0008-3 Revision No. 01 Effective Date: 06/22/2007 Page 12 of 29

Filtration mm Al Intensity decreases by ~40% for each additional mm Al

Worker size

(chest thickness) 

25–27 cm

>27 cm

ESE increased by factor of 1.5

ESE increased by factor of 2

Distance cm Approximately inverse square relations (1/d2)

Uncertainty ±30% Assume all errors are positive, +30% should be used

a. Source ORAUT (2005) 

3.3 X- RAY DOSES FROM 1951 TO PRESENT 

Extensive review of available documentation on the occupational medical program at NTS from 1951 

to the present revealed that two medical radiographic procedures were commonly administered in 

connection with preemployment, periodic, or postemployment medical examinations: 

1. 14- by 17-in. posterior-anterior (PA) chest films 

2. 14- by 17-in. lateral (LAT) chest films

Therefore, this analysis evaluated only doses from these two examinations (DeMarre 2002). Some of 

the claim file records have lumbar spine exams that may also have been performed for screening 

(especially during pre-employment physicals) as opposed to injury. Organ doses for lumbar spine 

exams can be found in ORAU-OTIB-0006 (ORAUT 2005). Other possible radiographic examinations 

of NTS employees may have been nonoccupational in the sense that they were necessitated by 

illness or injury, as many workers lived on site and were not part of the employee physical 

examination process DeMarre (2002). Information from NTS indicates that X-rays performed as a 

result of workplace accidents were administered offsite, by private contractors in the early years, 

before 1960 (Kathren and Shockley 2003). Also, there is no indication that radiological treatment for 

shrinkage of lymphoid tissue was ever performed on NTS workers [7]. 

A potential problem common to all procedures relates to the conversion of exposure represented by 

ESE to absorbed organ dose as well as to changes in the definition of dose and the creation of

numerous dose quantities. Over the 50 or so years since the beginning of NTS operations, the 

quantity known today as exposure has undergone several important conceptual changes, as has the 

application of the unit of exposure, the roentgen (R), which itself is obsolete. Thus, there is much 

confusion about the definition of exposure and the roentgen. At one time, the roentgen was used to 

quantify the dose from electromagnetic radiation and, when this proved confusing and inexact, was 

defined as exposure dose to distinguish it from the term absorbed dose, which was applicable to any 

type of radiation (Kathren and Peterson 1989). 

Additional confusion was engendered by changes in the values of the conversion coefficients used to 

convert exposure to absorbed dose. At various times, an exposure of 1 R would be equated to a soft 

tissue dose of 0.83, 0.877, or 0.93 rad. Therefore, an exposure in air of 1 R would result in an 

absorbed dose of somewhat less than 1 rad (1 cGy = 10 mGy). Nonetheless, external dosimetry 

regulations applicable to NTS and other DOE sites defined 1 R as exactly equal to a dose of 1 rad (10 

mGy =1 rem), thereby producing an overestimate in the reported dose or dose equivalent because 

dosimeters were typically calibrated against a field measured in roentgen, which was numerically 

equated to absorbed dose in rad (Kathren and Petersen 1989). 

A further complication in the conversion of ESE in terms of exposure to absorbed dose is the 

contemporary trend to refer to X-ray intensity in terms of the quantity kerma, which is measured in the 

same units as absorbed dose. The numerical value of kerma is, typically, slightly lower than the 

corresponding value of absorbed dose. Therefore, to ensure conservatism and compliance with 

OCAS-IG-001 (NIOSH 2006), and to avoid underestimation, 1 R of exposure was taken to be equal to 
Document No. ORAUT-TKBS-0008-3 Revision No. 01 Effective Date: 06/22/2007 Page 13 of 29

1 rad of absorbed dose and to 1 rad (10 mGy) of kerma (1 R = 1 rad = 1 rem has been used in other 

occupational medical TBDs) [8]. 

Conversion of exposure expressed as ESE was made in accordance with conversion coefficients 

published in Tables A2 through A8 of ICRP Publication 34 (ICRP 1982). These tables provide 

average absorbed organ doses for specific selected medical radiographic procedures related to an 

entrance air kerma without backscatter of 1 Gy for various beam qualities in terms of HVL of 

aluminum. However, the tables do not include all organs identified in the Interactive 

RadioEpidemiological Program (IREP) code. For organs included in the IREP but not specifically 

identified in ICRP Publication 34 (ICRP 1982), use of the dose conversion coefficient for the organ in 

ICRP Publication 34 (ICRP 1982) that is anatomically the closest is a reasonable and simple 

first-order approach that would generally be favorable to the claimant or neutral [9]. For example, the 

factor for lung would be applied to all other organs in the thoracic cavity (thymus, esophagus, liver, 

gall bladder, spleen, and stomach). Because an appreciable fraction of the skeleton, in particular the 

trabecular bone (which has a large surface-to-volume ratio) and the sternum (which is a primary 

location of red marrow in the adult), lies within the trunk, the factor for lung would also apply to bone 

surfaces. For organs in the abdomen (i.e., urinary bladder and colon/rectum), the dose conversion 

coefficient for ovaries would apply. For the eye and brain, the analogous organ is the thyroid. Table 

3-2 lists the analogues for IREP organs not included in ICRP Publication 34. [Figure 3-1 of (ORAUT 

2005) shows an organ diagram of the human torso].

Table 3-2. Analogues for IREP organs not in ICRP

Publication 34 (ICRP 1982). 

Anatomical

location

ICRP 34

Reference organ IREP organ analogues

Thorax Lung Thymus

Esophagus

Stomach

Bone surface

Liver/gall bladder/spleen

Remainder organs

Abdomen Ovaries Urinary/bladder

Colon/rectum

Head and neck Thyroid Eye/brain

Because, as discussed above, 1 R was taken to be 10 mGy of kerma, conversion could be made 

easily if the beam quality was known. Measured beam quality data were not found. However, the 

applied kilovoltage and filtration were known, and an estimate of beam quality could be made from 

these data. Because absorbed organ dose increases as a function of HVL for a given amount of 

filtration and exposure (milliampere-seconds), for conservatism, the upper limit on the likely beam 

quality was calculated and rounded upward to match the closest value in the tables in ICRP 

Publication 34 (ICRP 1982). For the period before 1957, beam quality expressed as HVL was 

conservatively estimated to be 2.5 mm Al. After 1957, the estimated HVL was 3.0 mm Al. These 

values are somewhat higher than the HVL values that would be derived from Table A16 of Publication 

34 and, therefore, are favorable to the claimant. The ESE was measured after January 1, 1957, to 

the present and this exposure used ICRP Publication 34 (ICRP 1982) DCFs from Tables A2. through 

A8 [10]. 

Table 3-3 lists the frequency of occupationally-required PA and LAT chest X-ray procedures for 

entrance (preemployment), exit (on leaving), and biennial (periodic) physical examinations from NTS 

information (Kathren and Shockley 2003). In the early years at the site, periodic X-ray examinations 

were provided on an annual basis for workers who were required to wear respiratory protection, on 
Document No. ORAUT-TKBS-0008-3 Revision No. 01 Effective Date: 06/22/2007 Page 14 of 29

employment, and on a 2-year frequency after that. In the early years, individuals in at-risk groups 

could have received medical examinations including X-rays at various, perhaps even more frequent, 

intervals. Such workers can be identified from specific medical records. Other employees neither 

working with radiation nor required to wear respiratory protection could have had X-rays on a 2-year 

frequency. The X-rays could have been both PA and LAT exposures for most workers when medical 

examinations were required. 

Table 3-3. Frequency of PA and LAT chest X-rays at NTS.

a

Period Frequency Comment

1951–1/1/1957d Entranceb,f All employees

Exitb All employees

Biennialc,f For workers respirator qualifiede

1/1/1957–Presentd Entranceb All employeesg

Exitb All employeesg

Biennial For workers respirator qualifiede

a. Source: Kathren and Shockley (2003). Frequency data provided from NTS X-ray 

records (DeMarre 2002–2003).

b. Entrance and exit X-rays were provided from 1951 to January 1, 1957. These X-rays 

were not required after 1980 unless personnel were in a job class that required an Xray. 

c. Older workers above age 45 might have been required to have X-ray examinations. 

Check worker file to verify before adding dose automatically.

d. Do not automatically add the LAT chest dose to the overall worker dose unless there 

is a record of the examination in the workers file [11].

e. Includes pulmonary function to determine lung function (capacity). Executive 

physical required this test if respiratory qualified.

f. Private contractors might have performed X-ray examinations off the site until the 

mid-1960s. 

g. Check workers personal file; workers normally did not have LAT X-ray examinations, 

and PA examinations might have been optional.

3.3.1

Table 3-4 summarizes the salient data for the 14- by 17-in. PA chest radiography. As indicated in the 

table, PA chest radiography was the most widely used screening procedure. Dates of measurement 

refer to the dates of measurement or estimate of machine output for the procedure specified. 

Generally, there is a decreasing trend of ESE with time, which is wholly consistent with national 

experience (Gray 1996). For conservatism in reconstructing doses and in accordance with the 

guidance in OCAS-IG-001 (NIOSH 2006), the ESE should be assumed to have been constant from 

the time of the measurement until the time of the next measurement [12]. Therefore, referring to 

Table 3-4, PA radiographs taken from 1951 to January 1, 1957 show an ESE of 125 mrem that was 

derived from BRH (1970), Gray (1996), and Geiger et al. (1960), and radiographs after 1957 show the 

measured ESE as 40 mrem (Kathren and Shockley 2003). 

Doses from Posterior-Anterior Chest Radiography 

As discussed in Section 3.2.4, this analysis includes the favorable to claimant assumption that 

minimal collimation occurred before January 1, 1957. Therefore, for procedures performed before 

January 1, 1957, substitute DCFs values were used (Table 3-5). The substitute DCFs were used to 

estimate the organ doses listed in Table 3-6 (which also lists those DCFs). 

Table 3-4. Beam parameters for 14- by 17-in. PA chest radiography.

a

Date measured 1951 to 1/1/1957 1/1/1957 to Present

Procedure Chest PA 14"×17" Chest PA 14"×17"

Machine type Standard X-ray Model # EC-200 Unknown

Machine settings 72 kVp Unknown

Current 200 mA Unknown

Exposure time 1/20 s Unknown
Document No. ORAUT-TKBS-0008-3 Revision No. 01 Effective Date: 06/22/2007 Page 15 of 29

Exposure 10 mAs Unknown

Added filter 2.0 mm Al 2.5 mm Al

HVL 2.5 mm Al 3.0 mm Al

SID 72 in. 72 in.

ESE 125 mR from Gray (1996)b 40 mR from film badge readingsc

a. Sources: BRH (1970), Gray (1996), Geiger et al. (1960), Kathren and Shockley (2003), and DeMarre (2002–2003). 

b. This value determined using information derived from Gray (1996) and Kathren and Shockley (2003). 

c. NTS Medical X-Ray equipment Geiger et al. (1960) and film badge readings from Kathren and Shockley (2003). 

Table 3-5. Substitute DCFs for PA and LAT chest projections assuming a minimally collimated beam. 

Organ of interest Substitute DCFs by organ and projection

Thyroid AP cervical spine corrected for depth by a factor of 0.2 [NCRP 

Report 102 (NRCP 1997, Table B.8, p. 103)] LAT cervical spine

Eye and brain PA and LAT skull, or PA chest, whichever is larger

Ovaries and analogues, testes, and uterus PA and LAT abdomen

Organ Dose Calculation Methods – Posterior–Anterior Chest Films

The organ doses for PA chest films were calculated using the exposure expressed as ESE multiplied 

by conversion coefficients in Tables A-2 through A-8 of ICRP Publication 34 (ICRP 1982). Table 3-6 

provides the organ dose information for each period that PA chest X-rays were performed on NTS 

workers. Because absorbed organ dose for PA chest radiographs for a given exposure and filtration 

will increase as a function of the HVL, two different values for HVL were used for dose determination. 

The HVLs were set at a reasonable maximum to ensure adequate doses were calculated. For the 

period before 1957, the estimated beam quality expressed as HVL was 2.5 mm Al; after 1957, 3.0 mm 

Al was used (see above for details).

The following are the methods used to calculate the dose in gray from Table 3-6 from 1951 to the 

present. It is important to note that the PA ESE of 125 mR assumed for 1951 to January 1, 1957, was 

derived using data from Geiger et al. (1960), BRH (1970), and Gray (1996) for dose calculation based 

on experience and references from the early 1940s as shown below: 

1951 to 

1/1/57

14- by 17-in. PA chest X-ray with 2.5-mm Al filter and an estimated ESE of 125 mR 

(0.00125 Gy ) (Gray 1996). This value is used with DCF values from Table 3-6 to 

estimate organ doses from PA chest X-rays. 

1/1/1957 to 

3/31/2004

14- by 17-in. PA chest X-ray with 3.0-mm Al filter and a measured ESE of 40 mR 

(0.0004 Gy) (Kathren and Shockley 2003). This value is used with DCFs from ICRP 

Publication 34 (ICRP 1982), Tables A-2 through A-8, to estimate the doses (mGy per 

Gy air kerma for a beam quality for 3.0 mm Al). 

Table 3-6. Organ doses from PA and LAT chest X-rays at NTS from 1951 to present. 

Organ

Chest 

projection

DCF (mGy per 

Gy air kerma)(a)

HVL 2.5 mm Al 

with minimal 

collimation

Organ dose for PA 

ESE= 125 mR; LAT 

ESE= 315 mR for 

1951 to 1/1/1957 

(rem)(b,c) with 

minimal collimation

DCF (mGy 

per Gy air 

kerma)(a)

HVL 3.0 mm 

Al with 

collimation

Organ dose for PA 

view ESE= 40 mR; 

LAT ESE= 100 mR for 

1/1/1957 to present

(rem)(b,c) with 

collimation

Thyroid PA 174d 2.17E-02 46 1.84E-03

LAT 137h 4.32E-02 133 1.33E-02

Eye/brain PA 32 4.00E-03 46 1.84E-03

LAT 137h 4.32E-02 133 1.33E-02

Ovaries PA 168e 2.1 E-02 1.8 7.20E-05
Document No. ORAUT-TKBS-0008-3 Revision No. 01 Effective Date: 06/22/2007 Page 16 of 29

LAT 57e 1.8 E-02 0.9 9.00E-05

Liver/gall 

bladder/spleen

PA 451 5.64E-02 535 2.14E-02

LAT 220 6.93E-02 267 2.67E-02

Urinary bladder PA 168e 2.1 E-02 1.8 7.20E-05

LAT 57e 1.8 E-02 0.9 9.00E-05

Colon rectum PA 168e 2.1 E-02 1.8 7.20E-05

LAT 57e 1.8 E-02 0.9 9.00E-05

Testes PA 9.1e 1.14 E-03 0.01 4.00E-07

LAT 3.3e 1.04 E-03 0.1 1.00E-05

Lungs (male) PA 419 5.24E-02 496 1.98E-02

LAT 193 6.08E-02 236 2.36E-02

Lungs (female) PA 451 5.64E-02 535 2.14E-02

LAT 220 6.93E-02 267 2.67E-02

Thymus PA 451 5.64E-02 535 2.14E-02

LAT 220 6.93E-02 267 2.67E-02

Esophagus PA 451 5.64E-02 535 2.14E-02

LAT 220 6.93E-02 267 2.67E-02

Stomach PA 451 5.64E-02 535 2.14E-02

LAT 220 6.93E-02 267 2.67E-02

Bone surfaces PA 451 5.64E-02 535 2.14E-02

LAT 220 6.93E-02 267 2.67E-02

Remainder PA 451 5.64E-02 535 2.14E-02

LAT 220 6.93E-02 267 2.67E-02

Breast PA 49 6.13E-03 69 2.76E-03

LAT 255 8.03E-02 287 2.87E-02

Uterus 

(embryo)

PA 149 1.86 E-02 2.3 9.20E-05

LAT 43 1.35 E-02 0.9 9.00E-05

Bone marrow 

(male)

PA 92 1.15E-02 117 4.68E-03

LAT 37 1.17E-02 48 4.80E-03

Bone marrow 

(female)

PA 86 1.08E-02 112 4.48E-03

LAT 29 9.14E-03 38 3.80E-03

Skin PA 1.35 × 125 mR 1.69E-01f 1.4 × 40 mR 5.60E-02g

LAT 1.35 × 315 mR 4.25E-01f 1.4 × 100 

mR

1.40E-01g

a. DCFs from Tables A.2 through A.8 of ICRP 34 (ICRP 1982). 

b. Source-to-image distance (SID) = 183 cm. 

c. Image Receptor Size (cm) 35.6 x 43.2. 

d. DCF for AP cervical spine corrected for depth by 0.2.

e. Substitute DCFs because of assumed poorly collimated beam.

f. Calculated using backscatter factor of 1.35 for HVL of 2.5 mm Al from NCRP Report 102 (NCRP 1997, Table B.8).

g. Calculated using backscatter factor of 1.40 for HVL of 4.0 mm Al from NCRP Report 102 (NCRP 1997, Table B.8).

h. DCF values are for LAT skull, used with minimal collimation for 1951 to 1957, as this results in doses favorable to the 

claimant.

3.3.2

Table 3-3 summarizes the period, frequency, and applicability for PA and LAT chest X-rays at NTS. 

Table 3-6 gives the information on ESE and organ doses for the LAT 14- by 17-in. chest projection. 

Although the LAT 14- by 17-in. chest projection was probably incorporated in the pre- and continuing 

employment physical examinations at NTS, LAT chest examinations were not always required on a 

regularly scheduled basis [13]. The dose to most organs from a LAT 14- by 17-in. chest radiograph is 

significantly greater than that from the more common 14- by 17-in. PA projection. All other factors 

notwithstanding, the ESE must of necessity be increased because of the greater body thickness 

Lateral 14- by 17-in. Chest Radiography
Document No. ORAUT-TKBS-0008-3 Revision No. 01 Effective Date: 06/22/2007 Page 17 of 29

presented laterally in comparison to PA. This means that the body will be closer to the X-ray tube and 

the exposure will increase due to the increased body thickness, which will further increase the ESE

(Sante 1946, Sante 1954). 

Few measurement data are available for LAT 14- by 17-in. chest projection at NTS [14]. Data by 

Kirklin et al. (1969) indicate that the ESE from a LAT radiograph was 1.94 times (approximately twice) 

the ESE from a PA chest radiograph. Depending on the degree of measurement error, this value 

could be slightly greater or smaller. Because other measurement data suggest that the ratio of ESE 

from LAT to PA chest radiographs could have been somewhat greater (Cardarelli et al. 2002; Rising 

and Soldat 1959; Stanford and Vance 1955), and to ensure that dose from this source was not 

underestimated, a moderately conservative factor of 2.5 was assumed for the ratio of ESE from LAT 

to PA chest projection for organ dose calculations (i.e., PA ESE times 2.5 was used as LAT ESE).

Organ Dose Calculation Methods – Lateral Chest Projection

The organ doses for LAT chest projection were calculated using the exposure expressed as ESE 

multiplied by conversion coefficients in Tables A-2 through A-8 of ICRP Publication 34 (ICRP 1982). 

Several of the above references support the use of a factor of 2.5 times the PA chest ESE for the LAT 

chest ESE, and this factor was used to determine doses for LAT chest radiographs for NTS workers 

for 1951 to the present. Because absorbed organ dose for LAT chest radiographs increases as a 

function of the HVL, which in turn is a function of the Al filter thickness used, two HVLs were used for 

dose determination. For the period before January 1, 1957, the estimated beam quality expressed as 

HVL is 2.5 mm Al; after January 1, 1957, the estimated HVL is 3.0 mm Al.

The following are the methods used to calculate the organ dose in gray from ESEs and DCFs listed in 

Table 3-6 (1951 to the present). The ESE for the LAT projection used for 1951 to January 1,1957, is 

2.5 times the assumed PA ESE of 125 mR, or 315 mR (rounded up) for the LAT chest radiograph. 

1951 to 

1/1/57

14- by 17-in. LAT chest X-ray with 2.5-mm Al filter and an assumed ESE of 315 mR

(0.00315 Gy). This value is used with DCF values from Table 3-6 to determine organ 

dose values for the listed organs in ICRP Publication 34 (ICRP 1982). 

1/1/57 to 

3/31/2004

14- by 17-in. LAT chest X-ray with 3-mm Al filter and a calculated ESE of 100 mR 

(0.001 Gy) (2.5 multiplied by 40 mR measured ESE). This value is used with DCF 

values from Tables A-2 through A-8 from ICRP Publication 34 (ICRP 1982). 

3.4 UNCERTAINTY ANALYSIS FOR RADIOGRAPHY DOSES 

Error (deviation from the correct, true, or conventionally accepted value of a quantity) and uncertainty

(defined in terms of the potential range of a stated, measured, assumed, or otherwise determined 

value of a quantity) provide an indication of the confidence of the dose estimates. Error implies 

knowledge of what the correct or actual value is, which is of course not known. Therefore, the more 

appropriate term is uncertainty, which is expressed in terms of a confidence level (e.g., a 99% 

confidence level indicates that the correct or true value, although not actually known, has a 99% 

probability of falling within the range cited) and includes both precision or reproducibility of the 

measurement and accuracy, or how close the measurement or estimate of dose comes to the actual 

or correct value [15]. 

In theory, a large number of factors can introduce uncertainties or affect the X-ray machine output 

intensity and dose to the worker. However, because X-ray doses at NTS were derived largely from 

actual beam intensity measurements, in practice, only five factors can be reasonably considered to 

have an impact on dose uncertainty: 
Document No. ORAUT-TKBS-0008-3 Revision No. 01 Effective Date: 06/22/2007 Page 18 of 29

1. Measurement error [16]

2. Variation in applied kilovoltage

3. Variation in beam current

4. Variation in exposure time

5. Distance from the worker to the source of the X-rays (SSD)

The influence of such other factors as use of screens, grids, reciprocity failure, film speed, and 

development issues, while potentially variable, would not affect the beam output intensity.

Medical X-ray doses at NTS were largely derived from actual measurement of X-ray machine output 

with R-meters or similar ionization chamber devices (Kathren and Shockley 2003). If properly 

calibrated and used, these typically and historically have had an uncertainty of ±2% for photon 

energies below 400 keV (Kathren and Larson 1969). Although more recent versions of these 

instruments might provide a somewhat smaller uncertainty, perhaps on the order of ±1% (NBS 1985, 

1988), for conservatism, the uncertainty range of ±2% should be applied to measurements of X-ray 

intensity at NTS [17]. 

For a given set of machine settings and parameters, X-ray output is theoretically constant and 

unvarying. However, this is not true in practice, although output is essentially constant unless focal 

spot loading occurs, as could be the case when the power rating of the machine is exceeded. It is 

unlikely that power ratings were ever exceeded because such an event would be difficult to achieve in 

practice and could result in damage to the X-ray tube. However, even with the use of constantvoltage transformers to control line voltages, slight variations can occur in line voltage input or other 

internal voltages, which in turn can alter the applied kilovoltage of the output beam. In general, for a 

given applied kilovoltage setting, variation falls within ±5% of the machine setting (Seibert, Barnes, 

and Gould 1991). As noted above, beam intensity is approximately proportional to the 1.7 power of 

the applied kilovoltage; this translates to an uncertainty of approximately ±8.6% in relation to output 

beam intensity in the 80- to 100-kVp range used for diagnostic chest radiographs at NTS. For 

conservatism, this is rounded up to ±9% [18]. 

Similarly, slight variations in tube current are normal; as a tube ages or heats up from use, current can 

change and typically drops. With all other factors constant, beam intensity is reduced in direct 

proportion to the change in tube current. Typically, the reduction in beam output from current 

variation is not more than a few percent under normal operating conditions; large decreases are 

readily detectable and manifest themselves as underexposed radiographs, which results in 

maintenance on the machine to restore the output or, as a temporary measure, an increase in the 

current or applied kilovoltage to provide the necessary intensity for proper radiography. There is no 

evidence to suggest that such temporary measures were ever necessary or used at NTS. For a given 

applied kilovoltage setting, the output of the beam is a function of the tube current, which is measured 

by a milliammeter that measures the average tube current. The measurement is subject to 

uncertainties; there can be minor changes in output as the tube heats from normal use. Because 

these variations are typically small, the estimated uncertainty in beam output attributable to current 

variation is conservatively taken to be ±5% [19]. 

Another parameter with the potential to affect the dose from a diagnostic radiograph, perhaps 

significantly, relates to the time of exposure. A full-wave-rectified machine produces 120 pulses per 

second of X-rays. In an exposure time of 1/20 of a second, only six pulses result. A small error in the 

timer that resulted in a change of only 1 pulse would correspondingly affect the output by ±17%; for an 

exposure time of 1/30 of a second, the change in output corresponding to a deviation of 1 pulse would 

be ±25%. Early mechanical timers were notoriously inaccurate; accuracy improved significantly with 

the introduction of electronic timers. Measurements of reproducibility made in the late 1980s and 
Document No. ORAUT-TKBS-0008-3 Revision No. 01 Effective Date: 06/22/2007 Page 19 of 29

beyond by the State of Washington for the machines at Hanford suggest that the timers, and indeed 

the entire X-ray output, were fairly constant (WDOH 1990–1999). However, for conservatism, the 

assumed uncertainty in beam output attributable to timers at NTS has an upper limit of ±25% [20]. 

The final factor likely to affect worker dose relates to distance from the source of the X-rays, which is 

a determinant of the ESE. For a given individual, the SSD will be determined largely by body 

thickness and the accuracy of the positioning. For a typical worker, the estimated variation in SSD is 

no more than a few centimeters with an upper limit of perhaps 7.5 cm. Using the inverse square, this 

indicates an uncertainty of ±10% from this source [21]. 

There are two approaches to determine the combined uncertainty from the five potential sources. The 

first, and most conservative in that it gives the greatest range, would be to assume that the 

uncertainties are additive, which would give an uncertainty range of ±51% (2 + 9 +5 + 25 + 10). 

However, a more reasonable approach would be to assume that the uncertainties are in fact random 

and to compute the statistical root mean square (RMS) value. The RMS value is simply the square 

root of the sum of the squares, and it computes as ±28.9%. Rounding this up to ±30% would seem to 

provide an adequate and suitably conservative indication of uncertainty. Therefore, for an individual 

ESE or derived organ dose, an uncertainty of ±30% can be assumed. For further conservatism, it 

would be appropriate to assume that errors are all positive, and only +30% should be used [22]. 

3.5 ATTRIBUTIONS AND ANNOTATIONS

Where appropriate in the preceding text, bracketed callouts have been inserted to indicate 

information, conclusions, and recommendations to assist in the process of worker dose 

reconstruction. These callouts are listed in this section with information that identifies the source and 

justification for each item. Conventional references are provided in the next section that link data, 

quotations, and other information to documents available for review on the Oak Ridge Associated 

Universities (ORAU) Team servers.

Vernon E. Shockley served as one of the initial Subject Experts for this document. Mr. Shockley was 

previously employed at NTS, and his work involved management, direction, or implementation of 

radiation protection and/or health physics program policies, procedures, or practices related to atomic 

weapons activities at the site. This revision has been overseen by a Document Owner who is fully 

responsible for the content, including all findings and conclusions. Mr. Shockley continues to serve as 

a Site Expert for this document because he possesses or is aware of information relevant to

reconstruction of radiation doses experienced by claimants who worked at the site. In all cases where 

such information or previous studies or writings are included or relied upon by Mr. Shockley, those 

materials are fully attributed to the source. Mr. Shockley’s Disclosure Statement is available at 

www.oraucoc.org. 

[1] Shockley, Vernon E. ORAU Team. Principal Health Physicist. March 2007. 

The statement on linearity is based on numerous conversations with Ronald Kathren in 

relation to his experience in measurement of personnel doses. He has indicated that they 

have clearly shown linearity. 

[2] Shockley, Vernon E.. ORAU Team. Principal Health Physicist. March 2007. 

Based on the knowledge, experience, and observations of Ronald Kathren. 

[3] Shockley, Vernon E. ORAU Team. Principal Health Physicist. March 2007. 

In 2002 and 2003, Martha DeMarre, Document Control Manager, Nuclear Testing Archives, 

Nevada Test Site (NTS) was contacted by the TBD Subject Expert. She had not and did not 
Document No. ORAUT-TKBS-0008-3 Revision No. 01 Effective Date: 06/22/2007 Page 20 of 29

find any information on the use of photofluorography (PFG) at the NTS. Ms. DeMarre had 

been working in Document Control at the NTS since the early 1960s, and she stated she had 

seen no indication in the files that NTS used PFG. 

[4] Shockley, Vernon E. ORAU Team. Principal Health Physicist. March 2007. 

This statement was provided by Ronald Kathren. There was no information found in the 

records that indicated NTS used a constant potential waveform X-ray machine. 

[5] Shockley, Vernon E. ORAU Team. Principal Health Physicist. March 2007. 

This statement was provided by Ronald Kathren. There was no information found in the 

records that indicated NTS used a constant potential waveform X-ray machine. 

[6] Shockley, Vernon E. ORAU Team. Principal Health Physicist. March 2007. 

DeMarre (2002–2003) indicates that NTS based X-ray doses on measurements of the X-ray 

beam with NTS film badges, which makes waveform of minor or little significance to the 

workers.

[7] Shockley, Vernon E. ORAU Team. Principal Health Physicist. March 2007. 

This statement is based on conversations with Ronald Kathren and his personal knowledge of 

this subject. No information has been found for the NTS that indicates otherwise.

[8] Shockley, Vernon E. ORAU Team. Principal Health Physicist. March 2007. 

This statement was made by Ron Kathren because this is required in 10 C.F.R. pt. 20 by the 

U.S. Nuclear Regulatory Commission. 

[9] Kathren, Ronald L., and Shockley, Vernon E. Kathren Group and ORAU Team. Consultant 

and Principal Health Physicist. June 2004. 

In conversations with Timothy Taulbee, he indicated that ORAUT-OTIB-0006 (ORAUT 2005) 

provided data to support the use of IREP code organs anatomically closest to the organ of 

interest. This is a reasonable method of determination. 

[10] Shockley, Vernon E. ORAU Team. Principal Health Physicist. March 2007. 

Discussions (e-mail and verbal) between Timothy Taulbee and Ronald Kathren resulted in the 

decision to use the beam quality of 2.5 mm Al HVL for years before 1957 at NTS. The DCFs 

based on this beam quality were conservative and favorable to claimants. After 1957 the 

beam quality was determined using an HVL of 3.0 mm Al. These DCF values were somewhat 

higher than the HVL values that would be derived using Table A16 of ICRP Publication 34 

(ICRP 1982) and are used because they are favorable to claimants. The ESE was measured 

after January 1, 1957, to the present using ICRP Publication 34 (ICRP 1982) DCFs from 

Tables A2 through A8. 

[11] Kathren, Ronald L., and Shockley, Vernon E. Kathren Group and ORAU Team. Consultant 

and Principal Health Physicist. March 2007. 

Discussion and e-mail correspondence with Martha DeMarre indicated that some LAT chest 

X-ray exams were provided, but not on a routine basis.

[12] Shockley, Vernon E. ORAU Team. Principal Health Physicist. March 2007. 

Based on discussion with Ronald Kathren about ESE measurement being constant from the 

time of one measurement to the next. This assumption ensures ESE doses are consistent 

and that the resulting organ doses remain consistent with OCAS-IG-001 guidance (NIOSH 

2006). 
Document No. ORAUT-TKBS-0008-3 Revision No. 01 Effective Date: 06/22/2007 Page 21 of 29

[13] Kathren, Ronald L., and Shockley, Vernon E. Kathren Group and ORAU Team. Consultant 

and Principal Health Physicist. March 2007. 

During discussions and e-mail correspondence with Martha DeMarre, she stated that the 

records show that PA chest X-rays were usually required for pre- and continuing physical 

exams, but LAT X-ray exams were not. 

[14] Kathren, Ronald L., and Shockley, Vernon E. Kathren Group and ORAU Team. Consultant 

and Principal Health Physicist. March 2007. 

Discussion and e-mail correspondence with Martha DeMarre indicated that some LAT chest 

X-ray exams were provided, but not on a routine basis. 

[15] Kathren, Ronald L., and Shockley, Vernon E. Kathren Group and ORAU Team. Consultant 

and Principal Health Physicist. March 2007. 

The information in the referenced documents for NTS is adequate to calculate doses that were 

received from occupationally required X-rays. There are uncertainties about how the 

measurements methods were performed to determine the total filtration values during this 

time. Therefore, an approach that is favorable to the claimants was used for this TBD. This 

approach included the calculation of the entrance kerma based on information in NCRP (1997, 

Table B.3) for the given kVp and a distance of 183 cm that was then corrected based on an 

assumed chest size of 24 cm with 5 cm between the chest and film using the inverse square 

law for point sources. This value was then corrected based on the provided current and 

exposure times. NCRP (1997, Table B.3) provides information based on a total filtration of 

2.5 mm Al. This was adjusted to account for the stated 1.5 mm Al based on the following 

formula where t is the thickness of aluminum in millimeters and I and Io are the beam 

intensities with and without the filter, respectively:

I = Ioe-0.4t

Given the uncertainty with measurements to determine the total filtration values, an 

assumption was made to apply DCFs based on 2.5-mm Al HVL in ICRP (1982), which is 

favorable to the claimants. 

[16] Kathren, Ronald L., and Shockley, Vernon E. Kathren Group and ORAU Team. Consultant 

and Principal Health Physicist. March 2007. 

The information in the referenced documents for NTS is adequate to calculate doses that were 

received from occupationally required X-rays. There are uncertainties about how the 

measurements methods were performed to determine the total filtration values during this 

time. Therefore, an approach that is favorable to the claimants was used for this TBD. This 

approach included the calculation of the entrance kerma based on information in NCRP (1997, 

Table B.3) for the given kVp and a distance of 183 cm that was then corrected based on an 

assumed chest size of 24 cm with 5 cm between the chest and film using the inverse square 

law for point sources. This value was then corrected based on the provided current and 

exposure times. NCRP (1997, Table B.3) provides information based on a total filtration of 

2.5 mm Al. This was adjusted to account for the stated 1.5 mm Al based on the following 

formula where t is the thickness of aluminum in millimeters and I and Io are the beam 

intensities with and without the filter, respectively:

I = Ioe-0.4t
Document No. ORAUT-TKBS-0008-3 Revision No. 01 Effective Date: 06/22/2007 Page 22 of 29

Given the uncertainty with measurements to determine the total filtration values, an 

assumption was made to apply DCFs based on 2.5-mm Al HVL in ICRP (1982), which is 

favorable to the claimants. 

[17] Shockley, Vernon E. Dade Moeller & Associates. Principal Health Physicist. March 2007. 

Discussions with Ronald Kathren indicated that the uncertainty might have become smaller, 

but the uncertainty remained in the TBD at ±5 % for conservatism and the difference is 

negligible.

[18] Kathren, Ronald L., and Shockley, Vernon E. Kathren Group and ORAU Team. Consultant 

and Principal Health Physicist. March 2007. 

The information in the referenced documents for NTS is adequate to calculate doses that were 

received from occupationally required X-rays. There are uncertainties about how the 

measurements methods were performed to determine the total filtration values during this 

time. Therefore, an approach that is favorable to the claimants was used for this TBD. This 

approach included the calculation of the entrance kerma based on information in NCRP (1997, 

Table B.3) for the given kVp and a distance of 183 cm that was then corrected based on an 

assumed chest size of 24 cm with 5 cm between the chest and film using the inverse square 

law for point sources. This value was then corrected based on the provided current and 

exposure times. NCRP (1997, Table B.3) provides information based on a total filtration of 

2.5 mm Al. This was adjusted to account for the stated 1.5 mm Al based on the following 

formula where t is the thickness of aluminum in millimeters and I and Io are the beam 

intensities with and without the filter, respectively:

I = Ioe-0.4t

Given the uncertainty with measurements to determine the total filtration values, an 

assumption was made to apply DCFs based on 2.5-mm Al HVL in ICRP (1982), which is 

favorable to the claimants. 

[19] Shockley, Vernon E. Dade Moeller & Associates. Principal Health Physicist. March 2007. 

Discussions with Ronald Kathren indicated that the uncertainty might have become smaller but 

the uncertainty remained in the TBD at ±5 % for conservatism and the difference is negligible. 

[20] Shockley, Vernon E. Dade Moeller & Associates. Principal Health Physicist. March 2007. 

Discussions with Ronald Kathren indicated that the uncertainty associated with timers might 

have become smaller but the uncertainty remained at ±25 % for conservatism and the 

difference is negligible because this is an upper limit.

[21] Kathren, Ronald L., and Shockley, Vernon E. Kathren Group and ORAU Team. Consultant 

and Principal Health Physicist. March 2007. 

The information in the referenced documents for NTS is adequate to calculate doses that were 

received from occupationally required X-rays. There are uncertainties about how the 

measurements methods were performed to determine the total filtration values during this 

time. Therefore, an approach that is favorable to the claimants was used for this TBD. This 

approach included the calculation of the entrance kerma based on information in NCRP (1997, 

Table B.3) for the given kVp and a distance of 183 cm that was then corrected based on an 

assumed chest size of 24 cm with 5 cm between the chest and film using the inverse square 

law for point sources. This value was then corrected based on the provided current and 

exposure times. NCRP (1997, Table B.3) provides information based on a total filtration of 

2.5 mm Al. This was adjusted to account for the stated 1.5 mm Al based on the following 
Document No. ORAUT-TKBS-0008-3 Revision No. 01 Effective Date: 06/22/2007 Page 23 of 29

formula where t is the thickness of aluminum in millimeters and I and Io are the beam 

intensities with and without the filter, respectively:

I = Ioe-0.4t

Given the uncertainty with measurements to determine the total filtration values, an 

assumption was made to apply DCFs based on 2.5-mm Al HVL in ICRP (1982), which is 

favorable to the claimants. 

[22] Shockley, Vernon E. Dade Moeller & Associates. Principal Health Physicist. March 2007. 

In discussions with Ronald Kathren, he indicated that the added uncertainties of ±51% do not 

take into consideration random uncertainties. Using the RMS values provides a more 

statistically accurate value of ±28.9%. Rounding this up to ±30% and assuming that +30% 

should be used is favorable to the claimant for dose reconstruction.
Document No. ORAUT-TKBS-0008-3 Revision No. 01 Effective Date: 06/22/2007 Page 24 of 29

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Exposure From Work-Related Chest X-Rays for Epidemiological Studies of Radiation 

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DeMarre, M. E., 2002, “Personal Communications through Electronic Mail, telephone and personal 

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Kathren, R. L., and V. E. Shockley, 2003, "Personal Communications with ME DeMarre re Medical XRays at NTS," memorandum to file, Oak Ridge Associated Universities Team, Oak Ridge, 

Tennessee, August 3.

Kirklin, C. W., B. D. Nuss, K. R. Heid, F. L. Rising, F. E. Adley, and E. B. Lavelle, 1969, “The AEC 

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from the Hanford Operations: Retrospective and Continuing Phases of Data Acquisition,” 

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Magie, W. F., 1896, "The Clinical Application of the Roentgen Rays, 1. The Use of Roentgen 

Apparatus," American Journal of Medical Science, volume 111, pp. 251–255.

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Commerce, Washington, D.C.

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Handbook 41, U.S. Department of Commerce, Washington, D.C., March 30.

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Commerce, Washington, D.C.

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250, U.S. Department of Commerce, Gaithersburg, Maryland.

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Instruments, Special Publication 250-16, U.S. Department of Commerce, Gaithersburg, 

Maryland.

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Gamma- Ray Protection for Energies Up To 10 MeV, Report 33, Washington, D.C.

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Protection and Measurement, Report 82, Bethesda, Maryland.

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NIOSH (National Institute for Occupational Safety and Health), 2006, External Dose Reconstruction 

Implementation Guideline, OCAS-IG-001, Rev. 2, Office of Compensation Analysis and 

Support, Cincinnati, Ohio, August 25. 

Olson, C. P., B. W. Trask, and E. L. Dessen, 1966, “Minor Command”, Chapter XXXVI, Radiology in 

World War II, A. L. Ahnfeldt, K. D. Allen, E. M. McFetridge, and M. W. Stein, editors, U.S. 

Department of the Army, Office of the Surgeon General, Washington, D.C.

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Related Diagnostic X-Ray Procedures, ORAUT-OTIB-0006, Rev. 03 PC-1, Oak Ridge, 

Tennessee, December 21.
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Rising, F. L., and J. K. Soldat (Battelle Northwest Health Physicists), 1959, “Radiation Exposures 

During Diagnostic Radiographic Examinations at Kadlec Methodist Hospital,” letter to Dr. W. 

D. Norwood (Hanford Medical Director), April 30. [SRDB Ref ID: 13343]

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Ann Arbor, Michigan.

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Quality Control of Diagnostic X-Ray Imaging Equipment, Medical Physics Monograph No. 20, 

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York.

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Organs of Workers During Routine Diagnostic X-Ray Examinations,” British Journal of 

Radiology, volume 28, pp. 266–273.

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Associated Universities Team) et al., National Institute for Occupational Safety and Health, 

Office of Compensation Analysis and Support, Cincinnati, Ohio, November 19. 

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Examinations,” American Journal of Roentgenology, Radium Therapy, and Nuclear Medicine, 

volume 78, number 6, pp. 983–987.

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Brothers, Ann Arbor, Michigan. 

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to the Patient in Diagnostic Roentgenology,” American Journal of Roentgenology, Radium 

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dated March 30, 1990, November 11, 1993, April 22, 1997, December 18, 1997, February 4, 

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Document No. ORAUT-TKBS-0008-3 Revision No. 01 Effective Date: 06/22/2007 Page 27 of 29

GLOSSARY

entrance skin exposure (ESE)

The exposure at the point where the X-ray beam enters the skin.

film speed

A measure of the sensitivity of the film to X-rays or light.

filtration

Material in the useful beam, which preferentially absorbs photons from the beam. 

focal spot

Apparent size of the area of the anode of an X-ray tube bombarded by accelerated electrons 

when viewed from the central axis of the useful radiation beam. 

fluence

A measure of the quantity of X-rays in a beam in diagnostic radiology, either particle fluence 

(the number of photons entering a sphere of unit cross-sectional area) or energy fluence (the 

sum of the energies of the photons passing through a unit area).

gray (Gy)

The special name for the SI unit of absorbed dose, kerma, and specific energy imparted equal 

to one (1) joule per kilogram (J/kg). (1 Gy = 1 J/kg = 100 rad). 

grid

A series of lead strips used to improve the quality of radiographic images by removing 

scattered X-rays. 

half-value layer (HVL)

Thickness of a specified substance which, when introduced into the path of a given beam of 

radiation, reduces the kerma rate by one-half (usually specified in mm Al). 

Interactive RadioEpidemiological Program (IREP)

A computer software program that uses information on the dose-response relationship and 

specific factors such as a claimant’s radiation exposure, gender, age at diagnosis, and age at 

exposure to calculate the probability of causation for a given pattern and level of radiation 

exposure.

International Commission on Radiological Protection (ICRP)

An independent international scientific body, established to advance for the public benefit the 

science of radiological protection, in particular by providing recommendations and guidance on 

all aspects of protection against ionizing radiation.

inverse square law

The mathematical relationship between the exposure rate from a point source of radiation and 

the distance from the source.

kerma

The sum of the initial kinetic energies of all the charged ionizing particles liberated by 

uncharged ionizing particles per unit mass of a specified material. 
Document No. ORAUT-TKBS-0008-3 Revision No. 01 Effective Date: 06/22/2007 Page 28 of 29

kiloelectron-volt (keV)

The energy equal to that acquired by a particle with one electron charge in passing through a 

potential difference of 1000 volts. 

milliammeter

An instrument for measuring electric current in milliamperes. 

National Council on Radiation Protection and Measurements (NCRP)

A nongovernmental, public service organization that formulates and disseminates information, 

guidance, and recommendations on radiation protection and measurements. 

organ dose

The dose to a given organ from an X-ray procedure.

photofluorography

An obsolete radiographic technique in which the image produced on a fluorescent screen by 

X-rays was photographed. 

photon

A quantum of electromagnetic radiation. 

posterior–anterior (PA)

A radiographic position in which the X-ray beam passes from posterior to the anterior side of 

the body. 

preemployment X-ray

A radiograph, usually a chest X-ray, taken before a worker is hired or assigned to a specific 

job used to screen for active disease. 

probability of causation (POC)

The probability or likelihood that a cancer was caused by occupational exposure to ionizing 

radiation. 

pulmonary

Relating to, functioning like, or associated with the lungs. 

radiograph

A photographic negative or image made with X-rays.

root mean square

The square root of the arithmetic mean of the squares of a set of numbers. 

screens

Fluorescent material in X-ray film cassettes that absorbs the X-rays and converts them into 

light that exposes the X-ray film.

source-to-image distance (SID)

The distance measured along the central ray from the center of the front of the surface of the 

source (focal spot) to the surface of the image detector. 
Document No. ORAUT-TKBS-0008-3 Revision No. 01 Effective Date: 06/22/2007 Page 29 of 29

source-to-skin distance (SSD)

The distance measured along the central ray from the center of the front of the surface of the 

source (focal spot) to the surface of the irradiated object or the patient. 

technique factors

The variables in machine setting [i.e., the peak voltage (kVp), current (mA), and time (s)] that 

are used for exposing a radiograph.

termination X-ray

An X-ray, usually a chest X-ray, that is taken when the employee is separated from the 

company.

tube current

Average electrical current measured in milliamperes from the cathode to the anode of an X-ray 

tube during operation of the tube. 

variable

A quantity that may assume any one of a set of values.

X-ray

Ionizing electromagnetic radiation originating outside the nucleus; also, a radiograph or 

photographic negative or image made with X-rays.

X-ray tube

An evacuated electronic tube in which X-rays are generated when electrons are accelerated 

by an applied voltage and strike an anode or target.